Electrical conductor



Nov. 17, 1936. L, WEA ER ET AL 2,060,914

ELECTRICAL CONDUCTOR a I Filed. Jan. 10, 1935 FIG. 1.

' INVENTORS 1.. L. WEAVER c. A. WEBBER ATTORNEY Patented Nov. 17, 1936 ELECTRICAL CONDUCTOR Leo L. Weaver, Cranford, and Carroll A. Webber,

Westfield, N. J. said Weaver assignor to Western Electric Company, Inc., New York, N. Y., a corporation of New York, and said Webber assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application January 10, 19%,Serial No. 1,104

Claims.

This invention relates to electrical conductors and more particularly to self coiling electrical conductor cords and to a method of making them.

It is desirable to have the ordinarily substantially llmply flexible conductor cords used on telephone subscribers sets-made elastically-retractile or self-coiling so that when not in use the cord will automatically coil itself into a compact and unobtrusive small bundle.

Que object of the present invention is to provide an improved self-coiling conductor cord for use in connection with telephone sets and in analogous applications.

in one embodiment thereof, the invention contemplates a coiling element to be associated with the electrical conductor strands within a conductor cord, comprising a precoiled, elastically tempered length of spring wire, in which the ends of the wire have been flattened to form slightly protruding corners and a tightly coiled helix of spring wire having the inner diameter of the helix such as to engage the corners above mentioned in the screw thread defined between. the colls'of the helix, screwed over each end of the coiling spring and extending out beyond the ends.

A sleeve of flexible wear resisting material such as a short length of tubular textile braid impregnated and coated with varnish is slipped over each of the terminal helices and a textile sheath braided over the whole.

Other objects and features of the invention will appear from the following detailed description of one embodiment thereof taken in connection with the accompanying drawing in which the same reference numerals are applied to identical parts in the several figures and in which Fig. 1 is a broken view in perspective of a telephone cord constructed in accordance with the invention;

Fig. 2 is an enlarged section on the line 22 of Fig. 1;

Fig. 3 is an enlarged view partly in longitudinal section of one end of the coiling element of Fig. 1,

and I Fig. 4 is an exploded-view of one end of the coiling spring and of the tight helix to be threaded thereon. I

In the embodiment of the invention herein disclosed, a suitable length of piano wire 20, or of material having similar elastic properties, is formed into a permanent elastically deformable helix, and its ends are flattened as at 2| to form corners 22 extending laterally beyond the normal contour of the wire. Another appropriate length of spring wire is formed into a tight helical coil .24 whose inner diameter approximates the diameter of the wire 20 and is less than the distance between the two corners 22, 22. This helix 25 is then put in place on the end of the Wire 20, as shown best in Fig. 3, by being screwed into place thereon, the corners 22, 22 engaging in the helical trough or space between the coils of the helix 24. Such a helix M is preferably placed over each end of the wire it. The outer end of each helix 24 is preferably also formed with an. axially oriented loop 25.

After the helices it, 24 are in place, textile threads or cords it, are secured to the loops 25, and then a protective sleeve '21 is slipped over each helix it. Each sleeve 2i may preferably be a short section of what is commercially known as varnish tubing, i. e. a length of braided textile tubing impregnated and coated with linseed oil varnish or cellulose acetate enamel or the like. A series of elements thus prepared is connected in sequence by the cords 26 being attached at each end to a first loop 250i one element and a last loop 25 of another forming a continuous chain of such elements. This chain is then fed through a. braiding machine and a continuous braided cover Ell formed thereon.

The customary three insulated electrical conductors Ml, till, lid for a telephone cord are then associated with the chain strand of coiling ele ments produced as described above and these four strands are then fed through a braiding machine 7 together and covered together with av braided textile sheath 29. When completed, the individual cord lengths are formed by cutting the whole midway between the ends of successive coiling elements. Each cord thus made is like that shown in Fig. 1. The coiling element 20 plus its end helices 24, 24 extends continuously throughout most but not all of the length of the cord, there being at each end a portion preferably some four to eight inches long extending beyond the ends of the helices 24, these parts being relatively limp and flexible as compared with the greater central length of the corclcontaining the coiling spring. Hence when the two ends of the cord are secured, e. g., to the receiver and base of the receiver.

1 vent the end of the core strand from damaging or kinking oi the cord over the ends of the spring ll and the sleeve 21 prevents the coils of the helices 24, 24 from nipping or unduly wearing the threads of the sheath 28.

The loops 25 and link threads 26 are not necessary but are convenient for continuous manufacture, as without them consecutive coil springs Ill must be fed at intervals by hand through a braider to receive the sheath 28.

The entirely limp sheath 28 outside of the loops 25 may be conveniently used as tie cords to fasten the ends 01 the cord in place and so relieve the conductors of any longitudinal jerks and strains in use.

Although herein disclosed as embodied in a over the core strand and flexible means on an end of the core strand within the sheath ,to prethe inside of the sheath.

2. In ,a sell coiling element for electrical conductors, anelastic coiled core strand,- a sheath over the core strand and means to prevent an end of the core strand from damaging the inside of the core strand sheath, the means comprising a strand coiled into a helix part of which encloses the end of the core strand,

3. In a sell coiling element for electrical conductors, an 'elasticcoiled core strand, a sheath over the core strand and means to prevent an end of the core strand from damaging the inside of the core strand sheath, the means comprising 'a strand coiled into a helix part of which encloses the end 0! the core strand, the end of the core strand being provided with projections engaging in the helical trough between adjacent coils of the helix thereon.

4. In a self coiling element for electrical conductors, an elastic coiled core strand, a sheath over the core strand and means to prevent an end of the core strand from damaging the inside of the core strand sheath, the means comprising a strand coiled into a helix part of which encloses the end 0! the core strand and an inner sheath over the last named helix and within the first named sheath.

5. In a sell coiling element for electrical conductors, an elastic coiled core strand, a sheath over the core strand and means to prevent an end of the core strand from damaging the inside of the core strand sheath, the means comprising a strand coiled into a helix part of which encloses the end oi the core strand and an inner sheath over the last named helix and within the first named sheath, the end of the core strand being provided with projections engaging in the helical trough between adjacent coils of the helix thereon.

6. A self coiling electrical conductor cord comprising an electrically conductive conductor strand, a coiling element having an elastic coiled core strand, a sheath over the core strand and means to prevent an end of the core strand from damaging the inside of the core strand sheath, the means comprising a strand coiled into a helix part or which encloses the end of the core strand.

2,060,914 The helices 24, 24 prevent any sharp bending and an outer sheath over both the conductor strand and the coiling element.

7. A self coiling electrical conductor cord comprising an electrically conductive conductor strand, a coiling element having an elastic coiled core strand, a sheath over the core strand and means to prevent an end of the core strand from damaging the inside of the core strand sheath, the means comprising a strand coiled into a helix part of which encloses the end oi the core strand. the end of the core strand being provided with projections engaging in the helical trough between adjacent coils oi the helix thereon, and an outer sheath over both the conductor strand and the coiling element.

8. A sell coiling electrical conductor cord comprising an electrically conductive conductor strand, a coiling element having an elastic coiled core strand, a sheath over the core strand and means to prevent an end of the core strand from damaging the inside oi the core strand sheath, the means comprising a strand coiled into a'hclix part of which encloses the end of the core strand and an inner sheath over the last named helix and within the first named sheath, and an outer sheath over both the conductor strand and thethe means comprising a strand coiled into a helix part of which encloses the end of the core strand and an inner sheath over the last named helix and within the first named sheath, the end of the core strand being provided with projections engaging'in the helical trough between adjacent coils of the helix thereon, and an outer sheath over both the conductor strand and the coiling element.

10. A self coiling electrical conductor cord comprising an electrically conductive conductor strand, a coiling element having an elastic coiled core strand, a sheath-over the core strand and means to prevent an end of the core strand from damaging the inside of the core strand sheath, the means comprising a strand coiled into a helix part 01 which encloses the end of the core strand, and an outer sheath over both the conductor strand and the coiling element. the conductor strand and the outer sheath extending beyond the free end of the helix on the end of the coiling element.

11. A self coiling electrical, conductor cord comprising an electrically conductive conductor strand, a coiling element having an elastic coiled core strand, a sheath over the core strand and means to prevent an end of the core strand from damaging the inside of the core strand sheath, the means comprising a strand coiled into a helix part of which encloses the end of the core strand, the end of the core strand being provided with projections engaging in the helical trough between adjacent coils oi the helix thereon, and an outer sheath over both the conductor strand and the coiling element, the conductor strand and the outer sheath extending beyond the free end of the helix on the end of the coiling element.

12. A self coiling electrical conductor cord comprising an electrically conductive conductor strand, a coiling element having an elastic coiled core strand. a sheath over the core strand and 7 helix and within the first named sheath,and an outer sheath over both the conductor strand and the coiling element, the conductor strand and the outer sheath extending beyond the free end of the helix on the end of the coiling element.

'13. A self coiling electrical conductor cord comprising an electrically conductive conductor strand, a coiling element having an elastic coiled core strand, a sheath over the core strand and means to prevent an end of the core strand from damaging the inside of the core strand sheath, the means comprising a strand coiled into a helix part 01' which encloses'the end of the core strand and an inner sheath over the last named helix and within the first named sheath, the end of the core strand being provided with projections engaging in the helical trough between adjacent coils of the helix thereon, and an outer sheath over both the conductor strand and the element, the conductor strand and the outer sheath extending beyond the free end oi the helix on the end oi the coiling element.

14. A method of making electrical conductor cords which includes the steps of forming a plurality of permanently helically coiled elastically deformable lengths of salt coiling strands, flexibly inter-linking the lengths of strand,iorming a continuous textile cover over .the lengths of strandand the links therebetween, forming a textile cover over the interlinked covered strands and a flexible electrical conductor placed in parallel with the strands and severing the assembly into separate self coiling cords.

15. An electrical conductor cord having acon ductlve strand, a self coiling strand assembled in parallel engagement therewith, a textile sheath over the self coiling strand individually, and tie-cords 'consisting of integral extensions of the sheath extending beyond the ends of the strand therein.

LEO L. WEAVER. CARROLL A. WEBBER. 

